Aerosol generating apparatus

ABSTRACT

An aerosol generating apparatus comprises: a power source; a load configured to have a resistance value that varies according to a temperature and generate an aerosol by atomizing an aerosol source or heating a flavor source when supplied with power from the power source; a sensor configured to include a resistor connected in series to the load and output a measurement value that is a current value of a current flowing through the resistor or a voltage value of a voltage applied to the resistor; and a control unit configured to control power supply from the power source to the load and receive output from the sensor, wherein the resistor has a resistance value that is set such that responsiveness of a change in the measurement value to a change in a temperature of the resistance value belongs to a prescribed range.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation of International Patent ApplicationNo. PCT/JP2017/038394 filed on Oct. 24, 2017, the entire disclosures ofwhich are incorporated herein by reference.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to an aerosol generating apparatus.

Description of the Related Art

Aerosol generating apparatuses (electronic vaporization apparatuses),such as so-called electronic cigarettes and nebulizers (inhalers), thatatomize (aerosolize) a liquid or a solid, which is an aerosol source,using a load that operates when supplied with power from a power source,such as a heater or an actuator, to allow a user to inhale the atomizedliquid or solid are known.

For example, a system for generating inhalable vapor using an electronicvaporization apparatus is proposed (for example, PTL1). With thistechnology, whether or not vaporization is occurring is determined bymonitoring power supplied to a coil that corresponds to a heater foratomizing an aerosol source. It is described that a reduction in powerrequired to keep the coil at a set temperature indicates that there isnot enough liquid in a fluid wick for normal vaporization to occur.

Also, an aerosol generating apparatus is proposed (for example, PTL2)that detects the presence of an aerosol forming substrate that includesor corresponds to an aerosol source in the proximity of a heatingelement configured to heat the aerosol forming substrate, by comparing,with a threshold value, power or energy that needs to be supplied to theheating element to keep the temperature of the heating element at atarget temperature.

CITATION LIST Patent Literature

PTL1: Japanese Patent Laid-Open No. 2017-501805

PTL2: Japanese Patent Laid-Open No. 2015-507476

PTL3: Japanese Patent Laid-Open No. 2005-525131

PTL4: Japanese Patent Laid-Open No. 2011-515093

PTL5: Japanese Patent Laid-Open No. 2013-509160

PTL6: Japanese Patent Laid-Open No. 2015-531600

PTL7: Japanese Patent Laid-Open No. 2014-501105

PTL8: Japanese Patent Laid-Open No. 2014-501106

PTL9: Japanese Patent Laid-Open No. 2014-501107

PTL10: International Publication No. 2017/021550

PTL11: Japanese Patent Laid-Open No. 2000-041654

PTL12: Japanese Patent Laid-Open No. 3-232481

PTL13: International Publication No. 2012/027350

PTL14: International Publication No. 1996/039879

PTL15: International Publication No. 2017/021550

When an aerosol is generated using an ordinary aerosol generatingapparatus, power supply from a power source to a heater is controlledsuch that the temperature of the heater is near the boiling point of anaerosol source. If a sufficient quantity of the aerosol source isremaining and the aerosol generation quantity is controlled, powersupplied from the power source to the heater has a constant value orshows a continuous change. In other words, if a sufficient quantity ofthe aerosol source is remaining and feedback control is performed tokeep the heater temperature at a target temperature or in a targettemperature range, power supplied from the power source to the heaterhas a constant value or shows a continuous change.

The remaining quantity of the aerosol source is an important variablethat is used in various kinds of control performed by the aerosolgenerating apparatus. If the remaining quantity of the aerosol source isnot detected or cannot be detected with sufficiently high precision, forexample, there is a risk that power supply from the power source to theheater will be continued even if the aerosol source has been alreadydepleted, and the charge amount of the power source will be wasted.

Therefore, the aerosol generating apparatus proposed in PTL2 determineswhether there is a sufficient quantity of the aerosol source based onpower required to maintain the temperature of the heater. However, poweris generally measured using a plurality of sensors, and it is difficultto accurately estimate the remaining quantity of the aerosol source ordepletion thereof based on the measured power unless errors of thesesensors are accurately calibrated or control that takes errors intoconsideration is established.

As other methods for detecting the remaining quantity of the aerosolsource, methods that use the temperature of the heater or the electricresistance value of the heater as described in PTL3 and PTL4 areproposed. It is known that the temperature and the electric resistancevalue of the heater take different values between a case in which asufficient quantity of the aerosol source is remaining and a case inwhich the aerosol source is depleted. However, dedicated sensors or aplurality of sensors are necessary for these methods, and therefore itis also difficult to accurately estimate the remaining quantity of theaerosol source or depletion thereof using these methods.

In a case in which a sensor does not have appropriate resolution, it hasbeen difficult to accurately detect a reduction in the remainingquantity, for example. Also, there has been a problem in that theaerosol is generated when the remaining quantity of the aerosol sourceetc. is measured using the sensor.

Therefore, the present invention aims to suppress generation of anaerosol in an aerosol generating apparatus during measurement or toimprove precision of estimation of the remaining quantity of an aerosolsource performed by the aerosol generating apparatus.

SUMMARY OF THE INVENTION

An aerosol generating apparatus according to the present inventionincludes a power source, a load configured to have a resistance valuethat varies according to a temperature and generate an aerosol byatomizing an aerosol source or heating a flavor source when suppliedwith power from the power source, a sensor configured to include aresistor connected in series to the load and output a measurement valuethat is a current value of a current flowing through the resistor or avoltage value of a voltage applied to the resistor, and a control unitconfigured to control power supply from the power source to the load andreceive output from the sensor, wherein the resistor has a resistancevalue that is set such that responsiveness of a change in themeasurement value to a change in a temperature of the resistance valuebelongs to a prescribed range.

The resistor has a resistance value that is set such that responsivenessof a change in the measurement value to a change in the temperature ofthe resistance value belongs to a prescribed range. If theresponsiveness is high, for example, the detection performance of thesensor is improved, but there is a risk that the aerosol will begenerated during measurement. To the contrary, if the responsiveness islow, the generation of the aerosol during measurement can be suppressed,but the detection performance of the sensor is also reduced. With theabove-described configuration, a well-balanced resistance value can beset.

A configuration is also possible in which the resistor has a resistancevalue that satisfies at least one of a first condition that a quantityof the aerosol generated by the load during a feeding period for whichpower is supplied from the power source to the resistor is not largerthan a threshold value, and a second condition that the control unit candetect a change in a remaining quantity of the aerosol source or theflavor source based on the measurement value. According to the firstcondition, generation of the aerosol during measurement can besuppressed, and according to the second condition, precision ofestimation of the remaining quantity of the aerosol source performed bythe aerosol generating apparatus can be improved.

The resistance value may be set to satisfy the first condition. Namely,a configuration is also possible in which the aerosol generatingapparatus further includes a mouthpiece end that is provided at an endportion of the aerosol generating apparatus to emit the aerosol, whereinthe threshold value is set such that the aerosol is not emitted from themouthpiece end during the feeding period. In other words, aconfiguration is also possible in which the threshold value is set suchthat heat generated by the load is not used for heat of evaporation ofthe aerosol source or the flavor source. A configuration is alsopossible in which the resistance value is set such that the aerosol isnot generated as a result of heat being generated by the load.

The resistance value may also be set to satisfy the second condition.Namely, a configuration is also possible in which the resistance valueis set such that the measurement value obtained when power supply to theload is started and the measurement value obtained when a remainingquantity of the aerosol source or the flavor source is not larger than aprescribed quantity differ from each other to be distinguishable for thecontrol unit. In other words, a configuration is also possible in whichthe resistance value is set such that an absolute value of a differencebetween the measurement value obtained when power supply to the load isstarted and the measurement value obtained when a remaining quantity ofthe aerosol source or the flavor source is not larger than a prescribedquantity is larger than resolution of the control unit. A configurationis also possible in which the resistance value is set such that themeasurement value obtained when the aerosol is generated and themeasurement value obtained when a remaining quantity of the aerosolsource or the flavor source is not larger than a prescribed quantitydiffer from each other to be distinguishable for the control unit. Aconfiguration is also possible in which the resistance value is set suchthat an absolute value of a difference between the measurement valueobtained when the aerosol is generated and the measurement valueobtained when a remaining quantity of the aerosol source or the flavorsource is not larger than a prescribed quantity is larger thanresolution of the control unit. A configuration is also possible inwhich the resistance value is set such that the measurement valueobtained when power supply to the load is started and the measurementvalue obtained when the aerosol is generated differ from each other tobe distinguishable for the control unit. A configuration is alsopossible in which the resistance value is set such that an absolutevalue of a difference between the measurement value obtained when powersupply to the load is started and the measurement value obtained whenthe aerosol is generated is larger than resolution of the control unit.

Alternatively, the resistance value satisfies the first condition andthe second condition. In this case, generation of the aerosol can besuppressed during measurement and precision of the remaining quantity ofthe aerosol source estimated by the aerosol generating apparatus can beimproved. Namely, two contradictory problems can be solved at the sametime.

A configuration is also possible in which the resistance value is closerto the largest value of values with which the second condition issatisfied than to the smallest value of values with which the firstcondition is satisfied. With this configuration, resolution regardingdetection of the remaining quantity can be improved as far as possiblewhile suppressing generation of the aerosol during measurement. Namely,resolution can be improved as far as possible while two contradictoryproblems are solved at the same time, and accordingly precision of theremaining quantity of the aerosol source estimated by the aerosolgenerating apparatus can be improved to the maximum extent.

A configuration is also possible in which the aerosol generatingapparatus further includes a feed circuit configured to electricallyconnect the power source to the load and include a first power supplypath for supplying power to the load not via the sensor and a secondpower supply path for supplying power to the load via the sensor.Specifically, such a configuration can be employed.

A configuration is also possible in which the feed circuit includes afirst node that is connected to the power source and from which the feedcircuit branches into the first power supply path and the second powersupply path, a second node that is provided downstream of the first nodeand at which the first power supply path and the second power supplypath merge with each other, and a linear regulator that is providedbetween the first node and the sensor on the second power supply path.With this configuration, the occurrence of conversion loss at the linearregulator can be eliminated from the first power supply path, andprecision of detection of the remaining quantity can be improved in thesecond power supply path.

An aerosol generating apparatus according to another aspect of thepresent invention includes a power source, a load configured to have aresistance value that varies according to a temperature and generate anaerosol by atomizing an aerosol source or heating a flavor source whensupplied with power from the power source, a sensor configured toinclude a resistor connected in series to the load and output ameasurement value that is a current value of a current flowing throughthe resistor or a voltage value of a voltage applied to the resistor,and a control unit configured to control power supply from the powersource to the load and receive output from the sensor, wherein theresistor has a resistance value that satisfies at least one of a firstcondition that a quantity of the aerosol generated by the load during afeeding period for which power is supplied from the power source to theresistor is not larger than a threshold value, and a second conditionthat a change in a remaining quantity of the aerosol source or theflavor source can be detected by the control unit based on themeasurement value.

According to the first condition, generation of the aerosol duringmeasurement can be suppressed, and according to the second condition,precision of estimation of the remaining quantity of the aerosol sourceperformed by the aerosol generating apparatus can be improved.

An aerosol generating apparatus according to another aspect of thepresent invention includes a power source, a load configured to have aresistance value that varies according to a temperature and generate anaerosol by atomizing an aerosol source or heating a flavor source whensupplied with power from the power source, a sensor configured toinclude a resistor connected in series to the load and output ameasurement value that is a current value of a current flowing throughthe resistance value or a voltage value of a voltage applied to theresistor, at least one adjustment resistor for adjusting magnitude of acurrent supplied to the load, and a control unit configured to controlpower supply from the power source to the load and receive output fromthe sensor, wherein resistance values of the resistor and the adjustmentresistor a first condition that a quantity of the aerosol generated bythe load during a feeding period for which power is supplied from thepower source to the load is not larger than a threshold value, and theresistor has a resistance value that is set such that responsiveness ofa change in the measurement value to a change in a temperature of theresistance value belongs to a prescribed range.

With this configuration, generation of the aerosol during measurementcan be suppressed or precision of the remaining quantity of the aerosolsource estimated by the aerosol generating apparatus can be improved, byusing the resistance value of the adjustment resistor in addition to theresistance value of the sensor.

A configuration is also possible in which the resistance value of theresistor is larger than the resistance value of the load. Thus,generation of the aerosol can be suppressed during measurement, forexample.

Note that what are described in the solution to problem can be combinedwithin a scope not departing from the problem to be solved by thepresent invention and the technical idea of the present invention. Also,what are described in the solution to problem can be provided as asystem that includes one or more apparatuses that include a computer, aprocessor, an electric circuit, etc., a method to be executed by anapparatus, or a program to be executed by an apparatus. The program canalso be executed on a network. A storage medium that holds the programmay also be provided.

According to the present invention, it is possible to suppressgeneration of the aerosol in the aerosol generating apparatus duringmeasurement, or improve precision of estimation of the remainingquantity of the aerosol source performed by the aerosol generatingapparatus.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments (with reference to theattached drawings).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing one example of the externalappearance of an aerosol generating apparatus.

FIG. 2 is an exploded view showing one example of the aerosol generatingapparatus.

FIG. 3 is a schematic diagram showing one example of an internalstructure of the aerosol generating apparatus.

FIG. 4 is a circuit diagram showing one example of a circuitconfiguration of the aerosol generating apparatus.

FIG. 5 is a block diagram showing processing for estimating the quantityof an aerosol source stored in a storage portion.

FIG. 6 is a processing flow diagram showing one example of remainingquantity estimation processing.

FIG. 7 is a timing chart showing one example of a state in which a useruses the aerosol generating apparatus.

FIG. 8 is a diagram showing one example of a method for determining thelength of a determination period.

FIG. 9 is a diagram showing another example of changes in the currentvalue of a current flowing through a load.

FIG. 10 is a processing flow diagram showing one example of processingfor setting the determination period.

FIG. 11 is a diagram schematically showing energy consumed at thestorage portion, a supply portion, and the load.

FIG. 12 is a graph schematically showing a relationship between energyconsumed at the load and the quantity of a generated aerosol.

FIG. 13 is one example of a graph showing a relationship between theremaining quantity of an aerosol source and the resistance value of theload.

FIG. 14 is a diagram showing a variation of a circuit included in theaerosol generating apparatus.

FIG. 15 is a diagram showing another variation of the circuit includedin the aerosol generating apparatus.

DESCRIPTION OF THE EMBODIMENTS

An embodiment of an aerosol generating apparatus according to thepresent invention will be described based on the drawings. Dimensions,materials, shapes, relative arrangements, etc. of constitutionalelements described in the present embodiment are examples. Also, theorder of processes is one example, and the order can be changed orprocesses can be executed in parallel within a scope not departing fromthe problem to be solved by the present invention and the technical ideaof the present invention. Therefore, the technical scope of the presentinvention is not limited to the following examples unless otherwisespecified.

Embodiment

FIG. 1 is a perspective view showing one example of the externalappearance of an aerosol generating apparatus. FIG. 2 is an explodedview showing one example of the aerosol generating apparatus. An aerosolgenerating apparatus 1 is an electronic cigarette, a nebulizer, etc. andgenerates an aerosol in response to inhalation performed by a user andprovides the aerosol to the user. Note that a single continuous inhalingaction performed by a user will be referred to as a “puff”. Also, in thepresent embodiment, the aerosol generating apparatus 1 adds a flavorcomponent etc. to the generated aerosol and emits the aerosol into themouth of the user.

As shown in FIGS. 1 and 2, the aerosol generating apparatus 1 includes amain body 2, an aerosol source holding portion 3, and an additivecomponent holding portion 4. The main body 2 supplies power and controlsoperations of the entire apparatus. The aerosol source holding portion 3holds an aerosol source to be atomized to generate an aerosol. Theadditive component holding portion 4 holds components such as a flavorcomponent, nicotine, etc. A user can inhale the aerosol with addedflavor etc. while holding a mouthpiece, which is an end portion on theadditive component holding portion 4 side, in their mouth.

The aerosol generating apparatus 1 is formed as a result of the mainbody 2, the aerosol source holding portion 3, and the additive componentholding portion 4 being assembled by the user, for example. In thepresent embodiment, the main body 2, the aerosol source holding portion3, and the additive component holding portion 4 have a cylindricalshape, a truncated cone shape, etc. with a predetermined diameter, andcan be coupled together in the order of the main body 2, the aerosolsource holding portion 3, and the additive component holding portion 4.The main body 2 and the aerosol source holding portion 3 are coupled toeach other by screwing together a male screw portion and a female screwportion that are respectively provided in end portions of the main body2 and the aerosol source holding portion 3, for example. The aerosolsource holding portion 3 and the additive component holding portion 4are coupled to each other by fitting the additive component holdingportion 4, which includes a side surface having tapers, into a tubularportion provided at one end of the aerosol source holding portion 3, forexample. The aerosol source holding portion 3 and the additive componentholding portion 4 may be disposable replacement parts.

<Internal Configuration>

FIG. 3 is a schematic diagram showing one example of the inside of theaerosol generating apparatus 1. The main body 2 includes a power source21, a control unit 22, and an inhalation sensor 23. The control unit 22is electrically connected to the power source 21 and the inhalationsensor 23. The power source 21 is a secondary battery, for example, andsupplies power to an electric circuit included in the aerosol generatingapparatus 1. The control unit 22 is a processor, such as amicrocontroller (MCU: Micro-Control Unit), and controls operations ofthe electric circuit included in the aerosol generating apparatus 1. Theinhalation sensor 23 is an air pressure sensor, a flow rate sensor, etc.When a user inhales from the mouthpiece of the aerosol generatingapparatus 1, the inhalation sensor 23 outputs a value according to anegative pressure or the flow rate of a gas flow generated inside theaerosol generating apparatus 1. Namely, the control unit 22 can detectinhalation based on the output value of the inhalation sensor 23.

The aerosol source holding portion 3 of the aerosol generating apparatus1 includes a storage portion 31, a supply portion 32, a load 33, and aremaining quantity sensor 34. The storage portion 31 is a container forstoring a liquid aerosol source to be atomized through heating. Notethat the aerosol source is a polyol-based material, such as glycerin orpropylene glycol, for example. The aerosol source may also be a liquidmixture (also referred to as a “flavor source”) that further contains anicotine liquid, water, a flavoring agent, etc. Assume that such anaerosol source is stored in the storage portion 31 in advance. Note thatthe aerosol source may also be a solid for which the storage portion 31is unnecessary.

The supply portion 32 includes a wick that is formed by twisting a fibermaterial, such as fiberglass, for example. The supply portion 32 isconnected to the storage portion 31. The supply portion 32 is alsoconnected to the load 33 or at least a portion of the supply portion 32is arranged in the vicinity of the load 33. The aerosol source permeatesthrough the wick by capillary action, and moves to a portion at whichthe aerosol source can be atomized as a result of being heated by theload 33. In other words, the supply portion 32 soaks up the aerosolsource from the storage portion 31 and carries the aerosol source to theload 33 or the vicinity of the load 33. Note that porous ceramic mayalso be used for the wick, instead of fiberglass.

The load 33 is a coil-shaped heater, for example, and generates heat asa result of a current flowing through the load 33. For example, the load33 has Positive Temperature Coefficient (PTC) characteristics, and theresistance value of the load 33 is substantially in direct proportion tothe generated heat temperature. Note that the load 33 does notnecessarily have to have Positive Temperature Coefficientcharacteristics, and it is only required that there is a correlationbetween the resistance value of the load 33 and the generated heattemperature. For example, a configuration is also possible in which theload 33 has Negative Temperature Coefficient (NTC) characteristics. Notethat the load 33 may be wrapped around the wick or conversely, thecircumference of the load 33 may be covered by the wick. The controlunit 22 controls power supply to the load 33. When the aerosol source issupplied from the storage portion 31 to the load 33 by the supplyportion 32, the aerosol source evaporates under heat generated by theload 33, and an aerosol is generated. If an inhaling action of the useris detected based on the output value of the inhalation sensor 23, thecontrol unit 22 supplies power to the load 33 to generate the aerosol.If the remaining quantity of the aerosol source stored in the storageportion 31 is sufficiently large, a sufficient quantity of the aerosolsource is supplied to the load 33 and heat generated by the load 33 istransferred to the aerosol source, in other words, heat generated by theload 33 is used for heating and vaporizing the aerosol source, andtherefore the temperature of the load 33 almost never becomes higherthan a predetermined temperature set in advance. On the other hand, ifthe aerosol source stored in the storage portion 31 is depleted, thequantity of the aerosol source supplied to the load 33 per unit timedecreases. As a result, heat generated by the load 33 is not transferredto the aerosol source, in other words, heat generated by the load 33 isnot used for heating and vaporizing the aerosol source, and thereforethe load 33 is excessively heated and the resistance value of the load33 is accordingly increased.

The remaining quantity sensor 34 outputs sensing data for estimating theremaining quantity of the aerosol source stored in the storage portion31 based on the temperature of the load 33. The remaining quantitysensor 34 includes, for example, a resistor (shunt resistor) that isconnected in series to the load 33 to measure a current, and ameasurement apparatus that is connected in parallel to the resistor tomeasure the voltage value of the resistor. Note that the resistancevalue of the resistor is a constant value that is determined in advanceand does not substantially vary according to the temperature. Therefore,the current value of a current flowing through the resistor can bedetermined based on the known resistance value and a measured voltagevalue.

Note that a measurement apparatus in which a hall element is used mayalso be used instead of the above-described measurement apparatus inwhich the shunt resistor is used. The hall element is arranged at aposition in series to the load 33. Namely, a gap core that includes thehall element is arranged around a conducting wire that is connected inseries to the load 33. The hall element detects a magnetic fieldgenerated by a current passing therethrough. In a case in which the hallelement is used, the “current passing therethrough” means a current thatflows through the conducting wire that is arranged at the center of thegap core and is not in contact with the hall element, and the currentvalue of the current is the same as that of a current flowing throughthe load 33. In the present embodiment, the remaining quantity sensor 34outputs the current value of a current flowing through the resistor.Alternatively, the voltage value of a voltage applied between oppositeends of the resistor may also be used, or a value obtained by performinga predetermined operation on the current value or the voltage value mayalso be used, rather than the current value or the voltage value itself.These measurement values that can be used instead of the current valueof a current flowing through the resistor are values that vary accordingto the current value of a current flowing through the resistor. Namely,the remaining quantity sensor 34 is only required to output ameasurement value corresponding to the current value of a currentflowing through the resistor. It goes without saying that the technicalidea of the present invention encompasses cases in which thesemeasurement values are used instead of the current value of a currentflowing through the resistor.

The additive component holding portion 4 of the aerosol generatingapparatus 1 holds chopped tobacco leaves and a flavor component 41, suchas menthol, therein. The additive component holding portion 4 includesair vents on the mouthpiece side and in a portion to be coupled to theaerosol source holding portion 3, and when the user inhales from themouthpiece, a negative pressure is generated inside the additivecomponent holding portion 4, the aerosol generated in the aerosol sourceholding portion 3 is sucked, nicotine, a flavor component, etc. areadded to the aerosol in the additive component holding portion 4, andthe aerosol is emitted into the mouth of the user.

Note that the internal configuration shown in FIG. 3 is one example. Aconfiguration is also possible in which the aerosol source holdingportion 3 is provided along a side surface of a cylinder and have atorus shape that includes a cavity extending along a center of acircular cross section. In this case, the supply portion 32 and the load33 may be arranged in the central cavity. Furthermore, an outputportion, such as an LED (Light Emitting Diode) or a vibrator, may befurther provided to output the state of the apparatus to the user.

<Circuit Configuration>

FIG. 4 is a circuit diagram showing one example of a portion of acircuit configuration in the aerosol generating apparatus relating todetection of the remaining quantity of the aerosol source and control ofpower supply to the load. The aerosol generating apparatus 1 includesthe power source 21, the control unit 22, a voltage conversion unit 211,switches (switching elements) Q1 and Q2, the load 33, and the remainingquantity sensor 34. A portion that connects the power source 21 to theload 33 and includes the switches Q1 and Q2 and the voltage conversionunit 211 will also be referred to as a “feed circuit” according to thepresent invention. The power source 21 and the control unit 22 areprovided in the main body 2 shown in FIGS. 1 to 3, and the voltageconversion unit 211, the switches Q1 and Q2, the load 33, and theremaining quantity sensor 34 are provided in the aerosol source holdingportion 3 shown in FIGS. 1 to 3, for example. As a result of the mainbody 2 and the aerosol source holding portion 3 being coupled together,constitutional elements therein are electrically connected to each otherand a circuit as shown in FIG. 4 is formed. Note that a configuration isalso possible in which at least some of the voltage conversion unit 211,the switches Q1 and Q2, and the remaining quantity sensor 34 areprovided in the main body 2, for example. In a case in which the aerosolsource holding portion 3 and the additive component holding portion 4are configured as disposable replacement parts, the cost of thereplacement parts can be reduced by reducing the number of componentsincluded in the replacement parts.

The power source 21 is directly or indirectly electrically connected toeach constitutional element and supplies power to the circuit. Thecontrol unit 22 is connected to the switches Q1 and Q2 and the remainingquantity sensor 34. The control unit 22 acquires an output value of theremaining quantity sensor 34 to calculate an estimated value regardingthe aerosol source remaining in the storage portion 31, and controlsopening and closing of the switches Q1 and Q2 based on the calculatedestimated value, an output value of the inhalation sensor 23, etc.

The switches Q1 and Q2 are semiconductor switches such as MOSFETs(Metal-Oxide-Semiconductor Field-Effect Transistors), for example. Oneend of the switch Q1 is connected to the power source 21 and another endof the switch Q1 is connected to the load 33. By closing the switch Q1,power can be supplied to the load 33 to generate an aerosol. The controlunit 22 closes the switch Q1 upon detecting an inhaling action of theuser, for example. Note that a path that passes the switch Q1 and theload 33 will also be referred to as an “aerosol generation path” and a“first power supply path”.

One end of the switch Q2 is connected to the power source 21 via thevoltage conversion unit 211 and another end of the switch Q2 isconnected to the load 33 via the remaining quantity sensor 34. Byclosing the switch Q2, an output value of the remaining quantity sensor34 can be acquired. Note that a path that passes the switch Q2, theremaining quantity sensor 34, and the load 33 and through which theremaining quantity sensor 34 outputs a prescribed measurement value willalso be referred to as a “remaining quantity detection path” and a“second power supply path” according to the present invention. Notethat, if a hall element is used in the remaining quantity sensor 34, theremaining quantity sensor 34 need not be connected to the switch Q2 andthe load 33 and is only required to be provided to be able to output aprescribed measurement value at a position between the switch Q2 and theload 33. In other words, it is only required that a conducting wire thatconnects the switch Q2 to the load 33 passes through the hall element.

The above-described circuit shown in FIG. 4 includes a first node 51from which a path extending from the power source 21 branches into theaerosol generation path and the remaining quantity detection path and asecond node 52 that is connected to the load 33 and at which the aerosolgeneration path and the remaining quantity detection path merge witheach other.

The voltage conversion unit 211 is capable of converting a voltageoutput by the power source 21 and outputting the converted voltage tothe load 33. Specifically, the voltage conversion unit 211 is a voltageregulator, such as an LDO (Low Drop-Out) regulator shown in FIG. 4, andoutputs a constant voltage. One end of the voltage conversion unit 211is connected to the power source 21 and another end of the voltageconversion unit 211 is connected to the switch Q2. The voltageconversion unit 211 includes a switch Q3, resistors R1 and R2,capacitors C1 and C2, a comparator Comp, and a constant voltage sourcethat outputs a reference voltage V_(REF). Note that, if the LDOregulator shown in FIG. 4 is used, an output voltage V_(out) of the LDOregulator can be determined using the following expression (1).

V _(out) =R ₂/(R ₁ +R ₂)×V _(REF)  (1)

The switch Q3 is a semiconductor switch, for example, and is opened orclosed according to output of the comparator Comp. One end of the switchQ3 is connected to the power source 21, and the output voltage ischanged according to the duty ratio of opening and closing of the switchQ3. The output voltage of the switch Q3 is divided by the resistors R₁and R₂ that are connected in series, and is applied to one inputterminal of the comparator Comp. The reference voltage V_(REF) isapplied to another input terminal of the comparator Comp. Then, a signalthat indicates the result of comparison between the reference voltageV_(REF) and the output voltage of the switch Q3 is output. Even if thevoltage value of a voltage applied to the switch Q3 varies, so long asthe voltage value is at least a predetermined value, the output voltageof the switch Q3 can be made constant based on feedback received fromthe comparator Comp, as described above. The comparator Comp and theswitch Q3 will also be referred to as a “voltage conversion unit”according to the present invention.

Note that one end of the capacitor C1 is connected to an end portion ofthe voltage conversion unit 211 on the power source 21 side and anotherend of the capacitor C1 is connected to the ground. The capacitor C1stores power and protects the circuit from a surge voltage. One end ofthe capacitor C2 is connected to an output terminal of the switch Q3 andthe capacitor C2 smooths the output voltage.

If a power source such as a secondary battery is used, the power sourcevoltage decreases as the charge rate decreases. With the voltageconversion unit 211 according to the present embodiment, a constantvoltage can be supplied even if the power source voltage varies to someextent.

The remaining quantity sensor 34 includes a shunt resistor 341 and avoltmeter 342. One end of the shunt resistor 341 is connected to thevoltage conversion unit 211 via the switch Q2. Another end of the shuntresistor 341 is connected to the load 33. Namely, the shunt resistor 341is connected in series to the load 33. The voltmeter 342 is connected inparallel to the shunt resistor 341 and is capable of measuring a voltagedrop amount at the shunt resistor 341. The voltmeter 342 is alsoconnected to the control unit 22 and outputs the measured voltage dropamount at the shunt resistor 341 to the control unit 22.

<Remaining Quantity Estimation Processing>

FIG. 5 is a block diagram showing processing for estimating the quantityof the aerosol source stored in the storage portion 31. Assume that avoltage V_(out) that is output by the voltage conversion unit 211 is aconstant. Also, a resistance value R_(shunt) of the shunt resistor 341is a known constant. Therefore, a current value I_(shunt) of a currentflowing through the shunt resistor 341 can be determined from a voltageV_(shunt) between opposite ends of the shunt resistor 341 using thefollowing expression (2).

I _(shunt) =V _(shunt) /R _(shunt)  (2)

Note that a current value I_(HTR) of a current flowing through the load33 connected in series to the shunt resistor 341 is equal to I_(shunt).The shunt resistor 341 is connected in series to the load 33, and avalue corresponding to the current value of a current flowing throughthe load is measured at the shunt resistor 341.

Here, the output voltage V_(out) of the voltage conversion unit 211 canbe expressed by the following expression (3) using a resistance valueR_(HTR) of the load 33.

V _(out) =I _(shunt)×(R _(shunt) +R _(HTR))  (3)

By transforming the expression (3), the resistance value R_(HTR) of theload 33 can be expressed by the following expression (4).

R _(HTR) =V _(out) /I _(shunt) −R _(shunt)  (4)

The load 33 has the above-described Positive Temperature Coefficient(PTC) characteristics, and the resistance value R_(HTR) of the load 33is substantially in direct proportion to a temperature T_(HTR) of theload 33 as shown in FIG. 5. Therefore, the temperature T_(HTR) of theload 33 can be calculated based on the resistance value R_(HTR) of theload 33. In the present embodiment, information that indicates arelationship between the resistance value R_(HTR) and the temperatureT_(HTR) of the load 33 is stored in a table in advance, for example.Therefore, the temperature T_(HTR) of the load 33 can be estimatedwithout using a dedicated temperature sensor. Note that, in a case inwhich the load 33 has Negative Temperature Coefficient (NTC)characteristics as well, the temperature T_(HTR) of the load 33 can beestimated based on information indicating a relationship between theresistance value R_(HTR) and the temperature T_(HTR).

In the present embodiment, even if the aerosol source around the load 33is evaporated by the load 33, the aerosol source is continuouslysupplied via the supply portion 32 to the load 33 so long as asufficient quantity of the aerosol source is stored in the storageportion 31. Therefore, if the quantity of the aerosol source remainingin the storage portion 31 is at least a predetermined quantity,normally, the temperature of the load 33 is not significantly increasedexceeding the boiling point of the aerosol source. However, as thequantity of the aerosol source remaining in the storage portion 31decreases, the quantity of the aerosol source supplied via the supplyportion 32 to the load 33 also decreases, and the temperature of theload 33 is increased exceeding the boiling point of the aerosol source.Assume that information that indicates such a relationship between theremaining quantity of the aerosol source and the temperature of the load33 is known in advance through experiments etc. Based on thisinformation and the calculated temperature T_(HTR) of the load 33, aremaining quantity of the aerosol source held by the storage portion 31can be estimated. Note that the remaining quantity may also bedetermined as the ratio of the remaining quantity to the capacity of thestorage portion 31.

Since there is a correlation between the remaining quantity of theaerosol source and the temperature of the load 33, it is possible todetermine that the aerosol source in the storage portion 31 is depletedif the temperature of the load 33 exceeds a threshold value of thetemperature that corresponds to a threshold value of the remainingquantity determined in advance. Furthermore, since there iscorrespondence between the resistance value and the temperature of theload 33, it is possible to determine that the aerosol source in thestorage portion 31 is depleted if the resistance value of the load 33exceeds a threshold value of the resistance value that corresponds tothe above-described threshold value of the temperature. Also, thecurrent value I_(shunt) of a current flowing through the shunt resistor341 is the only variable in the above-described expression (4), andaccordingly a threshold value of the current value that corresponds tothe above-described threshold value of the resistance value is uniquelydetermined. Here, the current value I_(shunt) of a current flowingthrough the shunt resistor 341 is equal to the current value I_(HTR) ofa current flowing through the load 33. Therefore, it is also possible todetermine that the aerosol source in the storage portion 31 is depletedif the current value I_(HTR) of a current flowing through the load 33 issmaller than a threshold value of the current value determined inadvance. Namely, with respect to a measurement value, such as thecurrent value of a current caused to flow through the load 33, it ispossible to determine a target value or a target range in a state inwhich a sufficient quantity of the aerosol source is remaining, forexample, and determine whether the remaining quantity of the aerosolsource is sufficiently large depending on whether or not the measurementvalue belongs to a prescribed range that includes the target value orthe target range. The prescribed range can be determined using theabove-described threshold value, for example.

As described above, according to the present embodiment, the resistancevalue R_(shunt) of the load 33 can be calculated using one measurementvalue, i.e., the value I_(shunt) of a current flowing through the shuntresistor 341. Note that the current value I_(shunt) of a current flowingthrough the shunt resistor 341 can be determined by measuring thevoltage V_(shunt) between opposite ends of the shunt resistor 341 asshown by the expression (2). Here, a measurement value output by asensor generally includes various errors, such as an offset error, again error, a hysteresis error, and a linearity error. In the presentembodiment, the voltage conversion unit 211 that outputs a constantvoltage is used, and accordingly, when estimating the remaining quantityof the aerosol source held by the storage portion 31 or determiningwhether or not the aerosol source in the storage portion 31 is depleted,the number of variables for which measurement values are to besubstituted is one. Therefore, precision of the calculated resistancevalue R_(HTR) of the load 33 is improved, when compared to a case inwhich the resistance value of the load etc. is calculated bysubstituting output values of different sensors for a plurality ofvariables, for example. As a result, precision of the remaining quantityof the aerosol source, which is estimated based on the resistance valueR_(HTR) of the load 33, is also improved.

FIG. 6 is a processing flow diagram showing one example of remainingquantity estimation processing. FIG. 7 is a timing chart showing oneexample of a state in which a user uses the aerosol generatingapparatus. In FIG. 7, the direction of an arrow indicates passage oftime t (s) and graphs respectively show opening and closing of theswitches Q1 and Q2, the value I_(HTR) of a current flowing through theload 33, the calculated temperature T_(HTR) of the load 33, and a changein the remaining quantity of the aerosol source. Note that thresholdvalues Thre1 and Thre2 are predetermined threshold values for detectingdepletion of the aerosol source. The aerosol generating apparatus 1estimates the remaining quantity when used by a user, and if a reductionin the aerosol source is detected, performs predetermined processing.

The control unit 22 of the aerosol generating apparatus 1 determineswhether the user has performed an inhaling action, based on output ofthe inhalation sensor 23 (FIG. 6: step S1). In this step, if the controlunit 22 detects generation of a negative pressure, a change in the flowrate, etc. based on output of the inhalation sensor 23, the control unit22 determines that an inhaling action of the user is detected. Ifinhalation is not detected (step S1: No), the process performed in stepS1 is repeated. Note that inhalation performed by the user may also bedetected by comparing a negative pressure or a change in the flow ratewith a threshold value other than 0.

On the other hand, if inhalation is detected (step S1: Yes), the controlunit 22 performs Pulse Width Modulation (PWM) control on the switch Q1(FIG. 6: step S2). Assume that inhalation is detected at time t1 in FIG.7, for example. After time t1, the control unit 22 opens and closes theswitch Q1 at a predetermined cycle. As the switch Q1 is opened andclosed, a current flows through the load 33 and the temperature T_(HTR)of the load 33 increases up to approximately the boiling point of theaerosol source. The aerosol source is heated with the temperature of theload 33 and evaporates, and the remaining quantity of the aerosol sourcedecreases. Note that Pulse Frequency Modulation (PFM) control may alsobe used, instead of the PWM control, when controlling the switch Q1 instep S2.

The control unit 22 determines whether the inhaling action of the userhas ended, based on output of the inhalation sensor 23 (FIG. 6: stepS3). In this step, the control unit 22 determines that the user hasceased to inhale if generation of a negative pressure, a change in theflow rate, etc. is no longer detected based on output of the inhalationsensor 23. If inhalation has not ended (step S3: No), the control unit22 repeats the process in step S2. Note that the end of the inhalingaction of the user may also be detected by comparing a negative pressureor a change in the flow rate with a threshold value other than 0.Alternatively, when a predetermined period has elapsed from detection ofthe inhaling action of the user in step S1, the processing may beadvanced to step S4 regardless of the determination made in step S3.

On the other hand, if inhalation has ended (step S3: Yes), the controlunit 22 ceases the PWM control of the switch Q1 (FIG. 6: step S4).Assume that it is determined at time t2 in FIG. 7 that inhalation hasended, for example. After time t2, the switch Q1 enters an open state(OFF) and power supply to the load 33 ceases. The aerosol source issupplied from the storage portion 31 via the supply portion 32 to theload 33 and the temperature T_(HTR) of the load 33 gradually decreasesthrough dissipation. As a result of the temperature T_(HTR) of the load33 decreasing, evaporation of the aerosol source ceases and a reductionin the remaining quantity also ceases.

As described above, as a result of the switch Q1 being turned ON, acurrent flows through the aerosol generation path shown in FIG. 4 insteps S2 to S4 surrounded by a rounded rectangle indicated by a dottedline in FIG. 6.

Thereafter, the control unit 22 continuously closes the switch Q2 for apredetermined period (FIG. 6: step S5). As a result of the switch Q2being turned ON, a current flows through the remaining quantitydetection path shown in FIG. 4 in steps S5 to S9 surrounded by a roundedrectangle indicated by a dotted line in FIG. 6. At time t3 in FIG. 7,the switch Q2 is in a closed state (ON). In the remaining quantitydetection path, the shunt resistor 341 is connected in series to theload 33. The remaining quantity detection path has a larger resistancevalue than the aerosol generation path as a result of the shunt resistor341 being added, and the current value I_(HTR) of a current flowingthrough the load 33 via the remaining quantity detection path is smallerthan the current value I_(HTR) of a current flowing through the load 33via the aerosol generation path.

In the state in which the switch Q2 is closed, the control unit 22acquires a measurement value from the remaining quantity sensor 34 anddetects the current value of a current flowing through the shuntresistor 341 (FIG. 6: step S6). In this step, the current valueI_(shunt) at the shunt resistor 341 is calculated using theabove-described expression (2) from a voltage between opposite ends ofthe shunt resistor 341 measured using the voltmeter 342, for example.Note that the current value I_(shunt) at the shunt resistor 341 is equalto the current value I_(HTR) of a current flowing through the load 33.

In the state in which the switch Q2 is closed, the control unit 22determines whether or not the current value of a current flowing throughthe load 33 is smaller than a threshold value of the current determinedin advance (FIG. 6: step S7). Namely, the control unit 22 determineswhether the measurement value belongs to a prescribed range thatincludes a target value or a target range. Here, the threshold value(FIG. 7: Thre1) of the current corresponds to a threshold value (FIG. 7:Thre2) of the remaining quantity of the aerosol source determined inadvance, with which it is to be determined that the aerosol source inthe storage portion 31 is depleted. Namely, if the current value I_(HTR)of a current flowing through the load 33 is smaller than the thresholdvalue Thre1, it is possible to determine that the remaining quantity ofthe aerosol source is smaller than the threshold value Thre2.

If the current value I_(HTR) becomes smaller than the threshold valueThre1 (step S7: Yes) within a predetermined period for which the switchQ2 is closed, the control unit 22 detects depletion of the aerosolsource and performs predetermined processing (FIG. 6: step S8). If thevoltage value measured in step S6 and the current value determined basedon the voltage value are smaller than predetermined threshold values,the remaining quantity of the aerosol source is small, and accordinglycontrol is performed in this step to further reduce the voltage valuemeasured in step S6 and the current value determined based on thevoltage value. For example, the control unit 22 may cease operations ofthe aerosol generating apparatus 1 by ceasing operations of the switchQ1 or Q2 or cutting off power supply to the load 33 using a power fuse(not shown), for example.

Note that, as is the case with the period from time t3 to time t4 inFIG. 7, if the remaining quantity of the aerosol source is sufficientlylarge, the current value I_(HTR) is larger than the threshold valueThre1.

After step S8 or if the current value I_(HTR) is at least the thresholdvalue Thre1 (step S7: No) over the predetermined period for which theswitch Q2 is closed, the control unit 22 opens the switch Q2 (FIG. 6:step S9). At time t4 in FIG. 7, the predetermined period has elapsed andthe current value I_(HTR) has been at least the threshold value Thre1,and therefore the switch Q2 is turned OFF. Note that the predeterminedperiod (corresponding to the period from time t3 to time t4 in FIG. 7)for which the switch Q2 is closed is shorter than a period(corresponding to the period from time t1 to time t2 in FIG. 7) forwhich the switch Q1 is closed in steps S2 to S4. If it is determined instep S7 that the measurement value belongs to the prescribed range, wheninhalation is detected thereafter (step S1: Yes), control is performedsuch that the current value (measurement value) to be calculated in stepS6 approaches the target value or the target range by opening andclosing the switch Q1 (step S2) while adjusting the duty ratio of theswitching, for example. Here, control is performed such that the amountof change in the measurement value is larger in a case in which the feedcircuit is controlled to reduce the amount of a current flowing to theload 33 (also referred to as a “second control mode” according to thepresent invention) when the measurement value does not belong to theprescribed range, than in a case in which the feed circuit is controlledto make the measurement value approach the target value or the targetrange (also referred to as a “first control mode” according to thepresent invention) when the measurement value belongs to the prescribedrange.

Thus, the remaining quantity estimation processing ends. Thereafter, theprocessing returns to the process performed in step S1, and if aninhaling action of the user is detected, the processing shown in FIG. 6is executed again.

At time t5 in FIG. 7, an inhaling action of the user is detected (FIG.6: step S1: Yes), and PWM control of the switch Q1 is started. At timet6 in FIG. 7, it is determined that the inhaling action of the user hasended (FIG. 6: step S3: Yes), and the PWM control of the switch Q1 isceased. At time t7 in FIG. 7, the switch Q2 is turned ON (FIG. 6: stepS5), and the current value at the shunt resistor is calculated (FIG. 6:step S6). Thereafter, as shown in the period after time t7 in FIG. 7,the remaining quantity of the aerosol source becomes smaller than thethreshold value Thre2 and the temperature T_(HTR) of the load 33increases. The current value I_(HTR) of a current flowing through theload 33 decreases, and at time t8, the control unit 22 detects that thecurrent value I_(HTR) is smaller than the threshold value Thre1 (FIG. 6:step S7: Yes). In this case, it is found that the aerosol cannot begenerated due to depletion of the aerosol source, and accordingly thecontrol unit 22 does not open and close the switch Q1 even if aninhaling action of the user is detected at time t8 or later, forexample. In the example shown in FIG. 7, the predetermined periodthereafter elapses at time t9, and the switch Q2 is turned OFF (FIG. 6:step S9). Note that the control unit 22 may also turn the switch Q2 OFFat time t8 at which the current value I_(HTR) becomes smaller than thethreshold value Thre1.

As described above, in the present embodiment, the voltage conversionunit 211 that converts voltage is provided, and therefore it is possibleto reduce errors that might be included in variables used for controlwhen estimating the remaining quantity of the aerosol source ordepletion thereof, and precision of control performed according to theremaining quantity of the aerosol source can be improved, for example.

<Determination Period>

In the remaining quantity determination processing performed in theabove-described embodiment, the control unit 22 acquires the measurementvalue of the remaining quantity sensor 34 while keeping the switch Q2 ONfor the predetermined period. Note that the period for which the switchQ2 is closed will be referred to as a “feeding sequence” for supplyingpower to the remaining quantity sensor 34 and the load 33. Here, a“determination period” for determining the remaining quantity of theaerosol source may also be used to determine the remaining quantity. Thedetermination period is included in the feeding sequence on a time axis,for example, and the length of the determination period is changeable.

FIG. 8 is a diagram showing one example of a method for determining thelength of the determination period. In the graph shown in FIG. 8, thehorizontal axis indicates passage of time t and the vertical axisindicates the current value I_(HTR) of a current flowing through theload 33. In the example shown in FIG. 8, the current value I_(HTR) of acurrent that flows when the switch Q1 is opened or closed is omitted forthe sake of convenience, and only the current value I_(HTR) of a currentthat flows through the load 33 in feeding sequences during which theswitch Q2 is closed is shown.

Periods p1 shown in FIG. 8 are normal feeding sequences, and the currentvalue I_(HTR) shown on the left represents a schematic profile in a casein which a sufficient quantity of the aerosol source is remaining.Assume that the determination period is initially equal to the feedingsequence (p1). In the example shown on the left, the temperature T_(HTR)of the load 33 increases as power is supplied, and the current valueI_(HTR) gradually decreases as a result of the resistance value R_(HTR)of the load 33 increasing with the increase in the temperature T_(HTR)of the load 33, but the current value I_(HTR) does not become smallerthan the threshold value Thre1. In such a case, the determination periodis not changed.

The current value I_(HTR) shown at the center represents a case in whichthe current value I_(HTR) becomes smaller than the threshold value Thre1within the determination period (p1). Here, a period p2 from the startof the feeding sequence to a time at which the current value I_(HTR)becomes smaller than the threshold value Thre1 is set as thedetermination period to be included in the following feeding sequence.Namely, the determination period in the following feeding sequence isadjusted based on the period it takes for the current value I_(HTR) tobecome smaller than the threshold value Thre1 in the preceding feedingsequence. In other words, the higher the possibility of depletion of theaerosol source is, the shorter the determination period is set. Aconfiguration is also possible in which the length of the feedingsequence is used as a reference, and if the current value I_(HTR)becomes smaller than the threshold value Thre1 within the feedingsequence (determination period), it is determined that the possibilityof depletion of the aerosol source is at least a threshold value (alsoreferred to as a “second threshold value” according to the presentinvention). In other words, the determination period is set to beshorter than the feeding sequence only when the possibility of depletionof the aerosol source is at least the threshold value.

The current value shown on the right represents a case in which thecurrent value I_(HTR) becomes smaller than the threshold value Thre1within the determination period (p2). The quantity of the aerosol sourceheld by the storage portion 31 continuously decreases while the aerosolgenerating apparatus 1 is used. Therefore, as the aerosol source isdepleted, the period from the start of power supply to a time at whichthe current value I_(HTR) becomes smaller than the threshold value Thre1normally gets shorter and shorter. In the example shown in FIG. 8, it isdetermined that the aerosol source is depleted (i.e., abnormal) if morethan a prescribed number of cases have consecutively occurred in whichthe current value I_(HTR) becomes smaller than the threshold value Thre1within the determination period, when the determination period isrepeated while being changed as described above. Note that, if theaerosol source is depleted, power supply to the remaining quantitydetection circuit may also be ceased as shown in FIG. 8.

FIG. 9 is a diagram showing another example of changes in the currentvalue of a current flowing through the load. The changes in the currentvalue I_(HTR) shown on the left and at the center of FIG. 9 are the sameas those shown in FIG. 8. The current value I_(HTR) shown on the rightof FIG. 9 has the same profile as that in the case in which a sufficientquantity of the aerosol source is remaining, and does not become smallerthan the threshold value Thre1 within the determination period (p2).Here, the aerosol generating apparatus 1 as shown in FIG. 3 isconfigured to supply the aerosol source from the storage portion 31 tothe supply portion 32 using capillary action, and therefore, dependingon the manner of inhalation performed by the user, it is difficult tocontrol supply of the aerosol source using the control unit 22 etc. Ifthe user inhales for a longer period than an envisaged period for asingle puff or inhales at a shorter interval than an envisaged normalinterval, the quantity of the aerosol source around the load 33 maytemporarily become smaller than a normal quantity. In such a case, thecurrent value I_(HTR) may become smaller than the threshold value Thre1within the determination period, as shown at the center of FIG. 9. Ifthe user thereafter inhales in a different manner, the current valueI_(HTR) does not become smaller than the threshold value Thre1 withinthe determination period, as shown on the right of FIG. 9. Therefore, inthe example shown in FIG. 9, the number of consecutive cases in whichthe current value I_(HTR) becomes smaller than the threshold value Thre1within the determination period is not larger than the prescribed numberwhen the determination period is repeated, and accordingly it isdetermined that the aerosol source stored in the storage portion 31 isnot depleted.

If the above-described determination period is employed, precision ofthe determination as to whether or not the aerosol source is depletedcan be further improved. Namely, the reference used in the determinationoperation can be adjusted by changing the determination period, andprecision of the determination can be improved.

<Variation of Determination Processing>

FIG. 10 is a processing flow diagram showing one example of processingfor setting the determination period. In this variation, the controlunit 22 executes determination processing shown in FIG. 10 instead ofthe processes performed in steps S5 to S9 in the remaining quantityestimation processing shown in FIG. 6.

First, the control unit 22 of the aerosol generating apparatus 1 turnsthe switch Q2 ON (FIG. 10: step S5). This step is the same as step S5 inFIG. 6.

Also, the control unit 22 activates a timer and starts to count anelapsed time t (FIG. 10: step S11).

Then, the control unit 22 determines whether the elapsed time t is atleast the determination period (FIG. 10: step S12). If the elapsed timet is shorter than the determination period (step S12: No), the controlunit 22 counts the elapsed time (FIG. 10: step S21). In this step, adifference Δt of a time elapsed from when the timer has been activatedor the process in step S21 has been previously performed is added to t.

Also, the control unit 22 detects the current value I_(HTR) of a currentflowing through the load 33 (FIG. 10: step S6). The process performed inthis step is the same as that performed in step S6 in FIG. 6.

Then, the control unit 22 determines whether the calculated currentvalue I_(HTR) is smaller than the predetermined threshold value Thre1(FIG. 10: step S7). This step is similar to step S7 in FIG. 6. If thecurrent value I_(HTR) is equal to or larger than the threshold valueThre1 (step S7: No), the processing returns to the process performed instep S12.

In contrast, if the current value I_(HTR) is smaller than the thresholdvalue Thre1 (step S7: Yes), the control unit 22 adds 1 to a counter forcounting the number of determination periods within which depletion isdetected (FIG. 10: step S22).

Then, the control unit 22 determines whether the counter indicates avalue that is larger than a prescribed value (threshold value) (stepS23). If it is determined that the counter indicates a value larger thanthe prescribed value (step S23: Yes), the control unit 22 determinesthat depletion of the aerosol source is detected, and performspredetermined processing (FIG. 10: step S8). This step is the same asstep S8 in FIG. 6.

In contrast, if it is determined that the counter indicates a value thatis not larger than the prescribed value (step S23: No), the control unit22 determines whether the feeding sequence has ended (FIG. 10: stepS31). If the feeding sequence has not elapsed (step S31: No), thecontrol unit 22 updates the elapsed time t and returns to the processperformed in step S31.

In contrast, if it is determined that the feeding sequence has ended(step S31: Yes), the control unit 22 updates the determination period(FIG. 10: step S32). In this step, the elapsed time t at the point intime when it is determined in step S7 that the current value I_(HTR) issmaller than the threshold value Thre1 is set as a new determinationperiod. Namely, the determination period in the following feedingsequence is adjusted based on the period it takes for the measurementvalue to become smaller than the threshold value in the precedingfeeding sequence. In other words, the length of the determination periodin the following feeding sequence is adjusted based on the measurementvalue obtained in the preceding feeding sequence. This can also be saidas adjusting the length of the determination period in a future feedingsequence based on the measurement value obtained in the current feedingsequence.

If it is determined in step S12 that the elapsed time t is at least thedetermination period (step S12: Yes), the control unit 22 determineswhether the feeding sequence has ended (FIG. 10: step S13). If thefeeding sequence has not ended (step S13: No), the control unit 22continues to supply power until the feeding sequence ends. A state inwhich the determination period has elapsed and the feeding sequence hasnot elapsed is the state after the period p2 has elapsed and before theperiod p1 elapses in the period shown on the right of FIG. 9.

If it is determined that the feeding sequence has ended (step S13: Yes),the control unit 22 sets the length of the determination period to beequal to the length of the feeding sequence (FIG. 10: step S14).

Also, the control unit 22 resets the counter (FIG. 10: step S15).Namely, the counter for counting the number of consecutive determinationperiods within which depletion is detected is reset because the currentvalue I_(HTR) has not become smaller than the threshold value Thre1within the determination period defined along with the feeding period.Note that a configuration is also possible in which the counter is notreset and, it is determined that there is an abnormality if the numberof determination periods within which depletion is detected exceeds apredetermined threshold value.

After step S15, S8, or S32, the control unit 22 turns the switch Q2 OFF(FIG. 10: step S9). This step is the same as step S9 in FIG. 6.

Through the above-described processing, the changeable determinationperiod shown in FIGS. 8 and 9 can be realized.

<Shunt Resistor>

The control unit 22 estimates the remaining quantity of the aerosolsource by causing the remaining quantity detection path to functionduring a period for which the user does not inhale using the aerosolgenerating apparatus 1. However, it is not preferable that the aerosolis emitted from the mouthpiece during the period for which the user doesnot inhale. Namely, it is desirable that the quantity of the aerosolsource evaporated by the load 33 while the switch Q2 is closed is assmall as possible.

On the other hand, it is preferable that the control unit 22 canprecisely detect a change in the remaining quantity of the aerosolsource when the remaining quantity is small. Namely, the resolutionincreases as the measurement value of the remaining quantity sensor 34largely changes according to the remaining quantity of the aerosolsource, which is desirable. The following describes the resistance valueof the shunt resistor based on these standpoints.

FIG. 11 is a diagram schematically showing energy consumed in thestorage portion, the supply portion, and the load. Q₁ represents thequantity of heat generated by the wick of the supply portion 32, Q₂represents the quantity of heat generated by the coil of the load 33, Q₃represents the quantity of heat required for increasing the temperatureof the aerosol source in a liquid state, Q₄ represents the quantity ofheat required for changing the aerosol source from the liquid state to agas state, and Q₅ represents heat generation in air through radiationetc. Consumed energy Q is the sum of Q₁ to Q₅.

The heat capacity C (J/K) of an object is a product of the mass m (g) ofthe object and the specific heat c (J/g·K) of the object. A heatquantity Q (J/K) required for changing the temperature of the object byT (K) can be expressed as m×C×T. Accordingly, if the temperature T_(HTR)of the load 33 is lower than the boiling point Tb of the aerosol source,the consumed energy Q can be schematically expressed by the followingexpression (6). Note that m₁ represents the mass of the wick of thesupply portion 32, C₁ represents the specific heat of the wick of thesupply portion 32, m₂ represents the mass of the coil of the load 33, C₂represents the specific heat of the coil of the load 33, m₃ representsthe mass of the aerosol source in the liquid state, C3 represents thespecific heat of the aerosol source in the liquid state, and T₀represents an initial value of the temperature of the load 33.

Q=(m ₁ C ₁ +m ₂ C ₂ +m ₃ C ₃)(T _(HTR) −T ₀)  (6)

If the temperature T_(HTR) of the load 33 is equal to or higher than theboiling point Tb of the aerosol source, the consumed energy Q can beexpressed by the following expression (7). Note that m₄ represents themass of an evaporated portion of the liquid aerosol source and H₄represents heat of evaporation of the liquid aerosol source.

Q=(m ₁ C ₁ +m ₂ C ₂)(T _(HTR) −T ₀)+m ₃ C ₃(T _(b) −T ₀)+m ₄ H ₄  (7)

Therefore, in order to prevent generation of the aerosol throughevaporation, a threshold value E_(thre) needs to satisfy a conditionshown by the following expression (8).

E _(thre)<(m ₁ C ₁ +m ₂ C ₂ +m ₃ C ₃)(T _(b) −T ₀)  (8)

FIG. 12 is a graph schematically showing a relationship between energy(electric energy) consumed by the load 33 and the quantity of thegenerated aerosol. In FIG. 12, the horizontal axis indicates the energyand the vertical axis indicates TPM (Total Particle Matter: the quantityof substances forming the aerosol). As shown in FIG. 12, generation ofthe aerosol starts when the energy consumed by the load 33 exceeds thepredetermined threshold value E_(thre), and the quantity of thegenerated aerosol increases substantially in direct proportion to theconsumed energy. Note that the vertical axis in FIG. 12 does notnecessarily have to indicate the quantity of the aerosol generated bythe load 33. For example, the vertical axis may also indicate thequantity of the aerosol generated through evaporation of the aerosolsource. Alternatively, the vertical axis may also indicate the quantityof the aerosol emitted from the mouthpiece.

Here, energy E_(HTR) consumed by the load 33 can be expressed by thefollowing expression (9). Note that WHIR represents the power of theload 33 and t_(Q2_ON) represents a period (s) for which the switch Q2 isturned ON. Note that the switch Q2 needs to be turned ON for a certainperiod to measure the current value at the shunt resistor.

E _(HTR) =W _(HTR) ×t _(Q2_ON)  (9)

The following expression (10) is obtained by transforming the expression(9) using a current value I_(Q2) of a current flowing through theremaining quantity detection path, a resistance value R_(HTR) (T_(HTR))of the load 33 that varies according to the temperature T_(HTR) of theload 33, and a measured voltage V_(meas) of the shunt resistor.

$\begin{matrix}\begin{matrix}{E_{HTR} = {W_{HTR} \times t_{Q{2\_}{ON}}}} \\{= {V_{HTR} \times I_{Q2} \times t_{Q{2\_}{ON}}}} \\{= {I_{Q2}^{2} \times {R_{HTR}( T_{HTR} )} \times t_{Q{2\_}{ON}}}} \\{= {( \frac{V_{meas}}{R_{shunt}} )^{2} \times {R_{HTR}( T_{HTR} )} \times t_{Q{2\_}{ON}}}}\end{matrix} & (10)\end{matrix}$

Therefore, if the energy E_(HTR) consumed by the load 33 is smaller thanthe threshold value E_(thre) shown in FIG. 12 as expressed by thefollowing expression (11), the aerosol is not generated.

$\begin{matrix}{E_{thre} > {( \frac{V_{meas}}{R_{shunt}} )^{2} \times {R_{HTR}( T_{HTR} )} \times t_{Q{2\_}{ON}}}} & (11)\end{matrix}$

This can be transformed to the following expression (12). Namely, if theresistance value R_(shunt) of the shunt resistor satisfies theexpression (12), the aerosol is not generated in the remaining quantityestimation processing, which is preferable.

$\begin{matrix}{R_{shunt} > {V_{meas}\sqrt{\frac{{R_{HTR}( T_{HTR} )} \times t_{Q{2\_}{ON}}}{E_{thre}}}}} & (12)\end{matrix}$

Generally, it is preferable that the shunt resistor has a smallresistance value, such as about several dozens of mΩ, to reduce effectson the circuit to which the shunt resistor is added. However, in thepresent embodiment, the lower limit of the resistance value of the shuntresistor is determined as described above from the standpoint ofsuppressing generation of the aerosol. The lower limit value ispreferably about several Ω, for example, which is larger than theresistance value of the load 33. As described above, the resistancevalue of the shunt resistor is preferably set to satisfy a firstcondition that the quantity of the aerosol generated by the load in thefeeding sequence during which power is supplied from the power source tothe resistor is not larger than a predetermined threshold value.

Note that a configuration is also possible in which the resistance valueof the shunt resistor is not increased, and an adjustment resistor isadditionally provided in series to the shunt resistor to increase thetotal resistance value. In this case, a configuration is also possiblein which a voltage between opposite ends of the added adjustmentresistor is not measured.

FIG. 13 is one example of a graph that shows a relationship between theremaining quantity of the aerosol source and the resistance value of theload 33. In the graph shown in FIG. 13, the horizontal axis indicatesthe remaining quantity of the aerosol source and the vertical axisindicates the resistance value of the load 33 determined according tothe temperature of the load 33. R_(HTR) (T_(Depletion)) represents aresistance value at a time when the aerosol source is depleted. R_(HTR)(T_(R.T.)) represents a resistance value at the room temperature. Here,precision of estimation of the remaining quantity of the aerosol sourcecan be improved by appropriately setting not only the voltage and thecurrent, but also a measurement range of the resistance value or thetemperature of the load 33, with respect to the resolution of thecontrol unit 22 including the number of bits. On the other hand, as thedifference between the resistance values R_(HTR) (T_(Depletion)) andR_(HTR) (T_(R.T.)) of the load 33 increases, the width of variationaccording to the remaining quantity of the aerosol source increases. Inother words, precision of the estimated value of the remaining quantitycalculated by the control unit 22 can be improved by increasing thewidth of variation of the resistance value of the load 33 that variesaccording to the temperature of the load 33, other than setting theresolution of the control unit 22 and the measurement range.

A current value I_(Q2_ON) (T_(Depletion)) that is detected based on anoutput value of the remaining quantity sensor 34 at a time when theaerosol source is depleted can be expressed by the following expression(13) using the resistance value R_(HTR) (T_(Depletion)) of the load 33at the time.

$\begin{matrix}{{I_{Q{2\_}{ON}}( T_{Depletion} )} = \frac{V_{out}}{R_{shunt} + {R_{HTR}( T_{D{epletion}} )}}} & (13)\end{matrix}$

Likewise, a current value I_(Q2_ON) (T_(R.T.)) that is detected based onan output value of the remaining quantity sensor 34 at a time when theload 33 is at the room temperature can be expressed by the followingexpression (14) using the resistance value R_(HTR) (T_(R.T.)) of theload 33 at the time.

$\begin{matrix}{{I_{Q{2\_}{ON}}( T_{R.T.} )} = \frac{V_{out}}{R_{shunt} + {R_{HTR}( T_{R.T.} )}}} & (14)\end{matrix}$

Further, a difference ΔI_(Q2_ON) obtained by subtracting the currentvalue I_(Q2_ON) (T_(Depletion)) from the current value I_(Q2_ON)(T_(R.T.)) can be expressed by the following expression (15).

$\begin{matrix}\begin{matrix}{{\Delta \; I_{Q{2\_}{ON}}} = {\frac{V_{out}}{R_{shunt} + {R_{HTR}( T_{R.T.} )}} - \frac{V_{out}}{R_{shunt} + {R_{HTR}( T_{Depletion} )}}}} \\{= \frac{\{ {{R_{HTR}( T_{D{epletion}} )} - {R_{HTR}( T_{R.T.} )}} \} \times V_{out}}{\{ {R_{shunt} + {R_{HTR}( T_{R.T.} )}} \} \times \{ {R_{shunt} + {R_{HTR}( T_{D{epletion}} )}} \}}}\end{matrix} & (15)\end{matrix}$

It can be found from the expression (15) that, if R_(shunt) isincreased, the difference ΔI_(Q2_ON) between the current value I_(Q2_ON)(T_(R.T.)) and the current value I_(Q2_ON) (T_(Depletion)) is reduced,and the remaining quantity of the aerosol source cannot be preciselyestimated. Therefore, the resistance value R_(shunt) of the shuntresistor is determined such that the difference ΔI_(Q2_ON) is largerthan a desired threshold value ΔI_(thre) as shown by the followingexpression (16).

$\begin{matrix}{{\Delta \; I_{thre}} < \frac{\{ {{R_{HTR}( T_{D{epletion}} )} - {R_{HTR}( T_{R.T.} )}} \} \times V_{out}}{\{ {R_{shunt} + {R_{HTR}( T_{R.T.} )}} \} \times \{ {R_{shunt} + {R_{HTR}( T_{D{epletion}} )}} \}}} & (16)\end{matrix}$

By solving the expression (16) with respect to the resistance valueR_(shunt), a condition that is to be satisfied by the resistance valueR_(shunt) to sufficiently increase the resolution regarding theestimated value of the remaining quantity can be expressed by thefollowing expression (17) using the desired threshold value ΔI_(thre).Therefore, the resistance value R_(shunt) is set to satisfy theexpression (17).

$\begin{matrix}{\mspace{79mu} {R_{shunt} < \frac{\sqrt{b^{2} - {4c}} - b}{2}}} & (17) \\{\mspace{79mu} {{b = {{R_{HTR}( T_{Depletion} )} + {R_{HTR}( T_{R.T.} )}}}{c = {{{R_{HTR}( T_{Depletion} )} \times {R_{HTR}( T_{R.T.} )}} + \frac{\{ {{R_{HTR}( T_{R.T.} )} - {R_{HTR}( T_{Depletion} )}} \} \times V_{out}}{\Delta \; I_{thre}}}}}} & \;\end{matrix}$

In the present embodiment, the resistance value R_(shunt) is set suchthat the difference ΔI_(Q2_ON) between the current value I_(Q2_ON)(T_(R.T.)) of a current flowing through the load 33 at the roomtemperature and the current value I_(Q2_ON) (T_(Depletion)) of a currentflowing through the load 33 when the aerosol source is depleted is largeenough to be detected by the control unit 22. Alternatively, aconfiguration is also possible in which the resistance value R_(shunt)is set such that a difference between the current value of a currentflowing through the load 33 at approximately the boiling point of theaerosol source and the current value of a current flowing through theload 33 when the aerosol source is depleted is large enough to bedetected by the control unit 22, for example. Generally, precision ofestimation of the remaining quantity of the aerosol source is improvedas the temperature difference corresponding to a current difference thatcan be detected by the control unit 22 is smaller.

The following more specifically describes effects that the resolution ofthe control unit 22 and settings of the remaining quantity detectioncircuit including the resistance value of the load 33 have on theprecision of estimation of the remaining quantity of the aerosol source.If an n-bit microcontroller is used for the control unit 22 and V_(REF)is applied as a reference voltage, the resolution of the control unit 22can be expressed by the following expression (18).

$\begin{matrix}{{Resolution}\mspace{11mu} {( {{V/b}it} ) = \frac{V_{REF}}{2^{n}}}} & (18)\end{matrix}$

A difference ΔV_(Q2_ON) between a value that is detected by thevoltmeter 342 when the load 33 is at the room temperature and a valuethat is detected by the voltmeter 342 when the aerosol source isdepleted can be expressed by the following expression (19) based on theexpression (15).

$\begin{matrix}{{\Delta \; V_{Q{2\_}{ON}}} = {{{\frac{R_{shunt}}{R_{shunt} + {R_{HTR}( T_{R.T.} )}} \times V_{out}} - {\frac{R_{shunt}}{R_{shunt} + {R_{HTR}( T_{Depletion} )}} \times V_{out}}} = {R_{shunt} \times V_{out} \times \{ {\frac{1}{R_{shunt} + {R_{HTR}( T_{R.T.} )}} - \frac{1}{R_{shunt} + {R_{HTR}( T_{Depletion} )}}} \}}}} & (19)\end{matrix}$

Therefore, according to the expressions (18) and (19), the control unit22 can detect a value expressed by the following expression (20) andintegral multiples of this value as voltage differences, in the rangefrom 0 to ΔV_(Q2_ON).

$\begin{matrix}{\frac{{{\Delta \; V_{Q{2\_}{ON}}} =}\;}{Resolution} = {2^{n} \times \frac{V_{out}}{V_{REF}} \times R_{shunt} \times \{ {\frac{1}{R_{shunt} + {R_{HTR}( T_{R.T.} )}} - \frac{1}{R_{shunt} + {R_{HTR}( T_{Depletion} )}}} \}}} & (20)\end{matrix}$

Furthermore, according to the expression (20), the control unit 22 candetect a value expressed by the following expression (21) and integralmultiples of this value as temperatures of the heater, in the range fromthe room temperature to the temperature of the load 33 at the time whenthe aerosol source is depleted.

$\begin{matrix}{\frac{( {T_{Depletion} - T_{R.T.}} ) \times {Resolution}}{\Delta \; V_{Q{2\_}{ON}}} = {\frac{( {T_{Depletion} - T_{R.T.}} ) \times V_{REF}}{2^{n} \times V_{out} \times R_{shunt}} \times \{ {\frac{1}{R_{shunt} + {R_{HTR}( T_{R.T.} )}} - \frac{1}{R_{shunt} + {R_{HTR}( T_{Depletion} )}}} \}^{- 1}}} & (21)\end{matrix}$

Table 1 below shows one example of the resolution of the control unit 22with respect to the temperature of the load 33 in cases in whichvariables in the expression (21) are changed.

TABLE 1 Varia- Varia- Varia- Varia- Varia- Variable [unit] tion 1 tion 2tion 3 tion 4 tion 5 T_(R) _(.T) _(.) [° C.] 25 25 25 25 25T_(Depletion) [° C.] 400 400 400 400 400 V_(REF) [V] 2 2 2 2 2 n [bit]10 10 16 10 8 V_(out) [V] 2.5 2.5 0.5 0.5 0.5 R_(shunt) [Ω] 3 10 3 3 3R_(HTR) (T_(R.T) _(.)) [Ω] 1 1 1 1 1 R_(HTR) (T_(Depletion)) [Ω] 2 2 1.51.5 1.5 Resolution [° C.] 2.0 3.9 0.3 17.6 70.3

As apparent from Table 1, there is a tendency that the resolution of thecontrol unit 22 with respect to the temperature of the load 33 largelychanges when values of the variables are adjusted. In order to determinewhether or not the aerosol source is depleted, the control unit 22 needsto be capable of distinguishing at least the room temperature, which isthe temperature at a time when control is not performed or is started bythe control unit 22, and the temperature at the time when the aerosolsource is depleted. Namely, a measurement value of the remainingquantity sensor 34 obtained at the room temperature and a measurementvalue of the remaining quantity sensor 34 obtained at the temperature atthe time when the aerosol source is depleted need to have a significantdifference therebetween to be distinguishable for the control unit 22.In other words, the resolution of the control unit 22 with respect tothe temperature of the load 33 needs to be not larger than a differencebetween the temperature at the time when the aerosol source is depletedand the room temperature.

As described above, if the remaining quantity of the aerosol source issufficiently large, the temperature of the load 33 is kept near theboiling point of the aerosol source. In order to more accuratelydetermine whether the aerosol source is depleted, it is preferable thatthe control unit 22 is capable of distinguishing the boiling point ofthe aerosol source and the temperature at the time when the aerosolsource is depleted. Namely, it is preferable that a measurement value ofthe remaining quantity sensor 34 obtained at the boiling point of theaerosol source and a measurement value of the remaining quantity sensor34 obtained at the temperature at the time when the aerosol source isdepleted have a significant difference therebetween to bedistinguishable for the control unit 22. In other words, it ispreferable that the resolution of the control unit 22 with respect tothe temperature of the load 33 is not larger than a difference betweenthe temperature at the time when the aerosol source is depleted and theboiling point of the aerosol source.

Furthermore, if the remaining quantity sensor 34 is used not only forobtaining a measurement value to be used for determining whether or notthe aerosol source is depleted, but also as a sensor for determining thetemperature of the load 33, it is preferable that the control unit 22 iscapable of distinguishing the room temperature, which is the temperatureat a time when control is not performed or is started by the controlunit 22, and the boiling point of the aerosol source. Namely, it ispreferable that a measurement value of the remaining quantity sensor 34obtained at the room temperature and a measurement value of theremaining quantity sensor 34 obtained at the boiling point of theaerosol source have a significant difference therebetween to bedistinguishable for the control unit 22. In other words, it ispreferable that the resolution of the control unit 22 with respect tothe temperature of the load 33 is not larger than a difference betweenthe boiling point of the aerosol source and the room temperature.

In order to use the remaining quantity sensor 34 for more preciselydetermining the temperature of the load 33, it is preferable that theresolution of the control unit 22 with respect to the temperature of theload 33 is not larger than 10° C. More preferably, the resolution is notlarger than 5° C. Further preferably, the resolution is not larger than1° C. In order to accurately distinguish a case in which the aerosolsource is going to be depleted and a case in which the aerosol sourcehas actually been depleted, it is preferable that the resolution of thecontrol unit 22 with respect to the temperature of the load 33 is adivisor of a difference between the temperature at the time when theaerosol source is depleted and the room temperature.

Note that, as apparent from Table 1, the resolution of the control unit22 with respect to the temperature of the load 33 can be easily improvedby increasing the number of bits of the control unit 22, in other words,by improving the performance of the control unit 22. However, anincrease in the performance of the control unit 22 leads to an increasein cost, weight, size, etc.

As described above, the resistance value of the shunt resistor can bedetermined to satisfy at least a first condition that the quantity ofthe aerosol generated by the load 33 is not larger than thepredetermined threshold value or a second condition that a reduction inthe remaining quantity of the aerosol source can be detected by thecontrol unit 22 based on an output value of the remaining quantitysensor 34, and it is more preferable that the resistance value of theshunt resistor is determined to satisfy both the first condition and thesecond condition. A configuration is also possible in which theresistance value of the shunt resistor is closer to the largest value ofvalues with which the second condition is satisfied than to the smallestvalue of values with which the first condition is satisfied. With thisconfiguration, the resolution regarding detection of the remainingquantity can be improved as far as possible while suppressing generationof the aerosol during measurement. As a result, the remaining quantityof the aerosol source can be estimated not only precisely but also in ashort period of time, and accordingly generation of the aerosol duringmeasurement can be further suppressed.

It can be said that both the first condition and the second conditionrelate to responsiveness of a change in the current value of a currentflowing through the load 33, which is the measurement value of theremaining quantity sensor 34, with respect to a change in thetemperature of the load 33. A case in which responsiveness of a changein the current value of a current flowing through the load 33 withrespect to a change in the temperature of the load 33 is strong is acase in which the load 33 is dominant in a combined resistanceconstituted by the shunt resistor 341 and the load 33 connected inseries. Namely, the resistance value R_(shunt) of the shunt resistor issmall, and therefore the second condition can be easily satisfied, butthe first condition is difficult to satisfy.

On the other hand, a case in which responsiveness of a change in thecurrent value of a current flowing through the load 33 with respect to achange in the temperature of the load 33 is weak is a case in which theshunt resistor 341 is dominant in the combined resistance constituted bythe shunt resistor 341 and the load 33 connected in series. Namely, theresistance value R_(shunt) of the shunt resistor is large, and thereforethe first condition can be easily satisfied, but the second condition isdifficult to satisfy.

Namely, in order to satisfy the first condition, responsiveness of achange in the current value of a current flowing through the load 33with respect to a change in the temperature of the load 33 needs to benot higher than a prescribed upper limit. On the other hand, in order tosatisfy the second condition, responsiveness of a change in the currentvalue of a current flowing through the load 33 with respect to a changein the temperature of the load 33 needs to be at least a prescribedlower limit. In order to satisfy both the first condition and the secondcondition, responsiveness of a change in the current value of a currentflowing through the load 33 with respect to a change in the temperatureof the load 33 needs to belong to a range that is defined by theprescribed upper limit and the prescribed lower limit.

<Circuit Variation 1>

FIG. 14 is a diagram showing a variation of the circuit included in theaerosol generating apparatus 1. In the example shown in FIG. 14, theremaining quantity detection path also serves as the aerosol generationpath. Namely, the voltage conversion unit 211, the switch Q2, theremaining quantity sensor 34, and the load 33 are connected in series.Generation of an aerosol and estimation of the remaining quantity areperformed using the single path. The remaining quantity can also beestimated with this configuration.

<Circuit Variation 2>

FIG. 15 is a diagram showing another variation of the circuit includedin the aerosol generating apparatus 1. The example shown in FIG. 15includes a voltage conversion unit 212 that is a switching regulator,instead of a linear regulator. In one example, the voltage conversionunit 212 is a step-up converter and includes an inductor L1, a diode D1,a switch Q4, and capacitors C1 and C2 that function as smoothingcapacitors. The voltage conversion unit 212 is provided upstream of aposition at which a path extending from the power source 21 branchesinto the aerosol generation path and the remaining quantity detectionpath. Accordingly, mutually different voltages can be respectivelyoutput to the aerosol generation path and the remaining quantitydetection path as a result of opening and closing of the switch Q4 ofthe voltage conversion unit 212 being controlled by the control unit 22.Note that, in a case in which a switching regulator is used instead of alinear regular as well, the switching regulator may be provided at thesame position as that of the linear regulator shown in FIG. 14.

A configuration is also possible in which the voltage conversion unit212 is controlled such that, when the aerosol generation path, which hasless restrictions regarding voltage applied thereto when compared to theremaining quantity detection path to the entirety of which a constantvoltage needs to be applied to detect the remaining quantity of theaerosol source, is caused to function, power loss is smaller than thatoccurs when the remaining quantity detection path is caused to function.With this configuration, wasting of the charge amount of the powersource 21 can be suppressed. Also, the control unit 22 performs controlsuch that a current that flows through the load 33 via the remainingquantity detection path is smaller than a current that flows through theload 33 via the aerosol generation path. Thus, generation of the aerosolat the load 33 can be suppressed while the remaining quantity of theaerosol source is estimated by causing the remaining quantity detectionpath to function.

A configuration is also possible in which, while the aerosol generationpath is caused to function, the switching regulator is caused to operatein a “direct coupling mode” (also referred to as a “direct couplingstate”) in which switching of the low side switch Q4 is ceased and theswitch Q4 is kept ON. Namely, the duty ratio of the switch Q4 may alsobe set to 100%. Loss that occurs when the switching regulator isswitched includes transition loss and switching loss that accompanyswitching, in addition to conduction loss. However, if the switchingregulator is caused to operate in the direct coupling mode, onlyconduction loss occurs at the switching regulator, and accordingly theuse efficiency of the charge amount of the power source 21 is improved.A configuration is also possible in which the switching regulator iscaused to operate in the direct coupling mode for a portion of a periodfor which the aerosol generation path is caused to function. In oneexample, if the charge amount of the power source 21 is sufficientlylarge and the output voltage of the power source 21 is high, theswitching regulator is caused to operate in the direct coupling mode. Onthe other hand, if the charge amount of the power source 21 is small andthe output voltage of the power source 21 is low, the switchingregulator may be switched. With this configuration as well, theremaining quantity can be estimated, and loss can be reduced whencompared to a case in which a linear regulator is used. Note that astep-down converter or a step-up/down converter may also be used insteadof a step-up converter.

<Others>

The target to be heated by the aerosol generating apparatus may be aliquid flavor source that contains nicotine and other additivematerials. In this case, a generated aerosol is inhaled by the userwithout passing through the additive component holding portion. In acase in which such a flavor source is used as well, the remainingquantity can be precisely estimated using the above-described aerosolgenerating apparatus.

The control unit 22 performs control such that the switches Q1 and Q2are not turned ON at the same time. Namely, the control unit 22 performscontrol such that the aerosol generation path and the remaining quantitydetection path do not function at the same time. A configuration is alsopossible in which a dead time for which both of the switches Q1 and Q2are turned OFF is provided when switching opening and closing of theswitches Q1 and Q2. This can prevent a situation in which a currentflows through the two paths. On the other hand, it is preferable to makethe dead time short to keep the temperature of the load 33 fromdecreasing during the dead time as far as possible.

The processing shown in FIG. 6 is described assuming that the remainingquantity estimation processing is performed one time for a single puffperformed by a user. However, a configuration is also possible in whichthe remaining quantity estimation processing is performed one time for aplurality of puffs, rather than being performed for every puff. Aconfiguration is also possible in which, after the aerosol sourceholding portion 3 is replaced, the remaining quantity estimationprocessing is started after a predetermined number of puffs, because asufficient quantity of the aerosol source is remaining after thereplacement. Namely, a configuration is also possible in which thefrequency of power supply to the remaining quantity detection path islower than the frequently of power supply to the aerosol generationpath. With this configuration, the remaining quantity estimationprocessing is kept from being excessively performed and is executed onlyat appropriate timings, and accordingly the use efficiency of the chargeamount of the power source 21 is improved.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all such modifications and equivalent structures andfunctions.

What is claimed is:
 1. An aerosol generating apparatus comprising: apower source; a load configured to have a resistance value that variesaccording to a temperature and generate an aerosol by atomizing anaerosol source or heating a flavor source when supplied with power fromthe power source; a sensor configured to include a resistor connected inseries to the load and output a measurement value that is a currentvalue of a current flowing through the resistor or a voltage value of avoltage applied to the resistor; and circuitry configured to controlpower supply from the power source to the load and receive output fromthe sensor, wherein the resistor has a resistance value that is set suchthat responsiveness of a change in the measurement value to a change ina temperature of the resistance value belongs to a prescribed range. 2.The aerosol generating apparatus of claim 1, wherein the resistor has aresistance value that satisfies at least one of: a first condition thata quantity of the aerosol generated by the load during a feeding periodfor which power is supplied from the power source to the resistor is notlarger than a threshold value, and a second condition that the circuitrycan detect a change in a remaining quantity of the aerosol source or theflavor source based on the measurement value.
 3. The aerosol generatingapparatus of claim 2, wherein the resistance value satisfies the firstcondition.
 4. The aerosol generating apparatus of claim 3, furthercomprising: a mouthpiece end that is provided at an end portion of theaerosol generating apparatus to emit the aerosol, wherein the thresholdvalue is set such that the aerosol is not emitted from the mouthpieceend during the feeding period.
 5. The aerosol generating apparatus ofclaim 3, wherein the threshold value is set such that energy supplied tothe load is not used for heat of evaporation of the aerosol source orthe flavor source.
 6. The aerosol generating apparatus of claim 3,wherein the threshold value is set such that the aerosol is notgenerated as a result of heat being generated by the load.
 7. Theaerosol generating apparatus of claim 2, wherein the resistance valuesatisfies the second condition.
 8. The aerosol generating apparatus ofclaim 7, wherein the resistance value is set such that the measurementvalue obtained when power supply to the load is started and themeasurement value obtained when a remaining quantity of the aerosolsource or the flavor source is not larger than a prescribed quantitydiffer from each other to be distinguishable for the circuitry.
 9. Theaerosol generating apparatus of claim 7, wherein the resistance value isset such that an absolute value of a difference between the measurementvalue obtained when power supply to the load is started and themeasurement value obtained when a remaining quantity of the aerosolsource or the flavor source is not larger than a prescribed quantity islarger than resolution of the circuitry.
 10. The aerosol generatingapparatus of claim 7, wherein the resistance value is set such that themeasurement value obtained when the aerosol is generated and themeasurement value obtained when a remaining quantity of the aerosolsource or the flavor source is not larger than a prescribed quantitydiffer from each other to be distinguishable for the circuitry.
 11. Theaerosol generating apparatus of claim 7, wherein the resistance value isset such that an absolute value of a difference between the measurementvalue obtained when the aerosol is generated and the measurement valueobtained when a remaining quantity of the aerosol source or the flavorsource is not larger than a prescribed quantity is larger thanresolution of the circuitry.
 12. The aerosol generating apparatus ofclaim 8, wherein the resistance value is set such that the measurementvalue obtained when power supply to the load is started and themeasurement value obtained when the aerosol is generated differ fromeach other to be distinguishable for the circuitry.
 13. The aerosolgenerating apparatus of claim 8, wherein the resistance value is setsuch that an absolute value of a difference between the measurementvalue obtained when power supply to the load is started and themeasurement value obtained when the aerosol is generated is larger thanresolution of the circuitry.
 14. The aerosol generating apparatus ofclaim 2, wherein the resistance value satisfies the first condition andthe second condition.
 15. The aerosol generating apparatus of claim 14,wherein the resistance value is closer to the largest value of valueswith which the second condition is satisfied than to the smallest valueof values with which the first condition is satisfied.
 16. The aerosolgenerating apparatus of claim 1, further comprising: a feed circuitconfigured to electrically connect the power source to the load andinclude a first power supply path for supplying power to the load notvia the sensor and a second power supply path for supplying power to theload via the sensor.
 17. The aerosol generating apparatus of claim 16,wherein the feed circuit includes: a first node that is connected to thepower source and from which the feed circuit branches into the firstpower supply path and the second power supply path; a second node thatis provided downstream of the first node and at which the first powersupply path and the second power supply path merge with each other; anda linear regulator that is provided between the first node and thesensor on the second power supply path.
 18. An aerosol generatingapparatus comprising: a power source; a load configured to have aresistance value that varies according to a temperature and generate anaerosol by atomizing an aerosol source or heating a flavor source whensupplied with power from the power source; a sensor configured toinclude a resistor connected in series to the load and output ameasurement value that is a current value of a current flowing throughthe resistor or a voltage value of a voltage applied to the resistor;and circuitry configured to control power supply from the power sourceto the load and receive output from the sensor, wherein the resistor hasa resistance value that satisfies at least one of a first condition thata quantity of the aerosol generated by the load during a feeding periodfor which power is supplied from the power source to the resistor is notlarger than a threshold value, and a second condition that a change in aremaining quantity of the aerosol source or the flavor source can bedetected by the circuitry based on the measurement value.
 19. An aerosolgenerating apparatus comprising: a power source; a load configured tohave a resistance value that varies according to a temperature andgenerate an aerosol by atomizing an aerosol source or heating a flavorsource when supplied with power from the power source; a sensorconfigured to include a resistor connected in series to the load andoutput a measurement value that is a current value of a current flowingthrough the resistance value or a voltage value of a voltage applied tothe resistor; at least one adjustment resistor for adjusting magnitudeof a current supplied to the load; and circuitry configured to controlpower supply from the power source to the load and receive output fromthe sensor, wherein resistance values of the resistor and the adjustmentresistor a first condition that a quantity of the aerosol generated bythe load during a feeding period for which power is supplied from thepower source to the load is not larger than a threshold value, and theresistor has a resistance value that is set such that responsiveness ofa change in the measurement value to a change in a temperature of theresistance value belongs to a prescribed range.
 20. The aerosolgenerating apparatus of claim 1, wherein a resistance value of theresistor is larger than a resistance value of the load.